Mission of the Month: May 2008
Invasive Species, The Aliens Around Us

We have explored outer space, inner space and now we are going to explore the space around us. Our environment includes all kinds of living things – the more the better! When there are lots of different kinds, we call it biodiversity.

Some of the things in our environment don’t really belong there naturally but were put there by people, either accidentally or on purpose. We call those introduced species. Sometimes people place things into different environments for what they think is a really good reason, but later it turns out to have been a mistake. When introduced species do so well in their new home that they start to badly affect the native plants, animals or fish, we call them invasive species.

What is an invasive species?

The natural environment around you is called your ecosystem. An ecosystem is a complex balance of living things. Introduced species, or non-indigenous species, can upset that balance. They sometimes push out the life that had been there. When they do, we call them invasive species.

Kudzu can grow out of control, choking trees and even covering buildings

People have moved plants and animals around for a long time. Ancient sailors carried plants and animals on their ships, and left some of these passengers behind in the places they visited. For example, scientists say that Hawaii has only two native mammals – a species of bat and one kind of seal. When new mammals were introduced, they didn’t have natural enemies. Sailors brought pigs to Hawaii and even today, wild pigs damage the Hawaiian environment because they will eat anything. In Australia, the problem species include rabbits and rats. With no natural enemies or diseases, these visitors’ populations grow unchecked and disrupt the food supply and ecosystem for the native populations.

Sometimes, invasive species are intentionally introduced. For example, the US government introduced an Asian plant called kudzu into the southeastern US. They thought it would provide cheap animal feed and control erosion on slopes. But kudzu grew so well that it is now a problem. It chokes out native plants, even covering trees and entire buildings if no one hacks it back!

About 100 years ago, the US government brought the carp, a relative of the goldfish from East Asia, to US lakes. They thought it would make a good and plentiful food. Izaak Walton, a famous naturalist, praised the fish, which was introduced to England about the same time,

“The Carp is the queen of rivers; a stately, a good, and a very subtil fish; that was not at first bred, nor hath been long in England, but is now naturalised.”

Carp thrive in North America, crowd out other species.

But the carp thrived too well in North American waters. Today, the carp is considered an invasive species across the US, as well as in Australia and many other countries. It out-breeds local fish in lakes and rivers, taking most of the resources. Many people don’t like the taste.

The carp and kudzu are examples of good intentions gone bad. Invasive species are hard to control. Large amounts of money and time get spent to control them, and to bring local species back.

What can you do?

Learn more about invasive species from these sources:
The Nature Conservancy’s Global Invasive Species Team: Invasives 101
The National Invasive Species Information Center
The USDA National Agriculture Library’s Invasive Species Information Center

This month's activities

Saldo Island, A Very Unfair Game
Which Aliens Live Near Me?
Invasive or Not?
Invasives Control: Learn, Debate Do Your Part